1. Field
Some example embodiments of the inventive concepts may relate generally to local tone mapping circuits. Some example embodiments of the inventive concepts may relate generally to local tone mapping circuits for reducing noise in signals that have been subjected to local tone mapping, by preventing noise in low-illumination regions of images from being boosted when the local tone mapping is performed on the low-illumination regions. Some example embodiments of the inventive concepts may relate generally to mobile computing devices including local tone mapping circuits.
2. Description of Related Art
High dynamic range (HDR) images may be images that contain various changes in grayscale (e.g., changes from darkest regions to brightest regions). HDR images may have large quantities of information and, thus, may require a dedicated viewer for HDR images. In order to watch HDR images using low dynamic range (LDR) displays which process 8-bit data, tone mapping processes may need to be performed.
Global tone mapping may include methods of using single tone mapping curves for entire image frames. These methods may use simple algorithms and may be easy to implement in real time. However, these methods may not adaptively reflect the local characteristics of images. On the contrary, local tone mapping may include methods of using different parameters in non-linear functions for each pixel. These methods well reflect local characteristics of images, thereby providing images having better rendering results than global tone mapping. In other words, local tone mapping may provide images having brightness with contrast improved based on local characteristics of the images.
However, when large tone mapping gain values are used to increase the brightness of low-illumination regions of images in local tone mapping, there may be problems in that noise in the low-illumination regions may also be boosted as the low-illumination regions are brightened.